Shockwave balloon catheter system

ABSTRACT

A system for breaking obstructions in body lumens includes a catheter including an elongated carrier, a balloon about the carrier in sealed relation thereto, the balloon being arranged to receive a fluid therein that inflates the balloon, and an arc generator including at least one electrode within the balloon that forms a mechanical shock wave within the balloon. The system further includes a power source that provides electrical energy to the arc generator.

PRIORITY CLAIM

The present application claims the benefit of copending U.S. ProvisionalPatent Application Ser. No. 60/061,170, filed Jun. 13, 2008, whichapplication is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a treatment system for percutaneouscoronary angioplasty or peripheral angioplasty in which a dilationcatheter is used to cross a lesion in order to dilate the lesion andrestore normal blood flow in the artery. It is particularly useful whenthe lesion is a calcified lesion in the wall of the artery. Calcifiedlesions require high pressures (sometimes as high as 10-15 or even 30atmospheres) to break the calcified plaque and push it back into thevessel wall. With such pressures comes trauma to the vessel wall whichcan contribute to vessel rebound, dissection, thrombus formation, and ahigh level of restenosis. Non-concentric calcified lesions can result inundue stress to the free wall of the vessel when exposed to highpressures. An angioplasty balloon when inflated to high pressures canhave a specific maximum diameter to which it will expand but the openingin the vessel under a concentric lesion will typically be much smaller.As the pressure is increased to open the passage way for blood theballoon will be confined to the size of the open in the calcified lesion(before it is broken open). As the pressure builds a tremendous amountof energy is stored in the balloon until the calcified lesion breaks orcracks. That energy is then released and results in the rapid expansionof the balloon to its maximum dimension and may stress and injure thevessel walls.

SUMMARY OF THE INVENTION

The invention provides a catheter that comprises an elongated carrier, adilating balloon about the carrier in sealed relation thereto, theballoon being arranged to receive a fluid therein that inflates theballoon, and an arc generator including at least one electrode withinthe balloon that forms a mechanical shock wave within the balloon.

The at least one electrode may include a single metallic electrode of apair of metallic electrodes. The electrodes may be radially displacedfrom each other or longitudinally displaced from each other. The atleast one electrode may be formed of stainless steel.

The balloon may be formed of non-compliant material or of compliantmaterial. The dilating balloon may have at least one stress risercarried on its surface.

The catheter may further comprise a sensor that senses reflected energy.The sensor may be distal to the at least one electrode. The sensor maybe disposed on the carrier.

The catheter may further comprise a reflector within the dilatingballoon that focuses the shock waves. The reflector may form one of theat least one electrodes. The catheter has a center line and thereflector may be arranged to focus the shock waves off of the cathetercenter line.

The fluid may be saline. The fluid may include an x-ray contrast.

The catheter may further include a lumen for receiving a guide wire. Thelumen may be defined by the carrier.

The invention further provides a system comprising a catheter includingan elongated carrier, a dilating balloon about the carrier in sealedrelation thereto, the balloon being arranged to receive a fluid thereinthat inflates the balloon, and an arc generator including at least oneelectrode within the balloon that forms a mechanical shock wave withinthe balloon. The system further comprises a power source that provideselectrical energy to the arc generator.

The power source is preferably arranged to provide pulsed high voltage.The power source may be arranged to provide high voltage pulses havingselectable pulse durations, selectable voltage amplitudes, and/orselectable pulse repetition rates.

The system may further comprise an R wave detector that synchronizes themechanical shock waves with cardiac R waves.

The at least one electrode may include a single metallic electrode of apair of metallic electrodes. The electrodes may be radially displacedfrom each other or longitudinally displaced from each other. The atleast one electrode may be formed of stainless steel.

The balloon may be formed of non-compliant material or of compliantmaterial. The dilating balloon may have at least one stress risercarried on its surface.

The catheter may further comprise a sensor that senses reflected energy.The sensor may be distal to the at least one electrode. The sensor maybe disposed on the carrier.

The catheter may further comprise a reflector within the dilatingballoon that focuses the shock waves. The reflector may form one of theat least one electrodes. The catheter has a center line and thereflector may be arranged to focus the shock waves off of the cathetercenter line.

The fluid may be saline. The fluid may include an x-ray contrast.

The catheter may further include a lumen for receiving a guide wire. Thelumen may be defined by the carrier.

The invention further provides a method comprising the step of providinga catheter including an elongated carrier, a dilating balloon about thecarrier in sealed relation thereto, the balloon being arranged toreceive a fluid therein that inflates the balloon, and an arc generatorincluding at least one electrode within the balloon that forms amechanical shock wave within the balloon. The method further comprisesthe steps of inserting the catheter into a body lumen of a patientadjacent an obstruction of the body lumen, admitting fluid into theballoon, and applying high voltage pulses to the arc generator to form aseries of mechanical shocks within the balloon.

The method may include the further step of detecting cardiac R waves ofthe patient's heart, and synchronizing the mechanical shocks with thedetected R waves.

The method may further include the step of varying one of the repetitionrate, amplitude and duration of the high voltage pulses to vary theintensity of the mechanical shock waves.

The method may include the further step of sensing reflected energywithin the catheter.

The method may include the further step of placing a guide wire into thebody lumen and guiding the catheter into the body lumen along the guidewire.

The method may include the further step of focusing the mechanicalshockwaves. The mechanical shockwaves may be focused away from thecatheter center axis.

The method may include the further steps of adding an x-ray contrast tothe fluid and visualizing the catheter under fluoroscopy.

BRIEF DESCRIPTION OF THE DRAWINGS

For illustration and not limitation, some of the features of the presentinvention are set forth in the appended claims. The various embodimentsof the invention, together with representative features and advantagesthereof, may best be understood by making reference to the followingdescription taken in conjunction with the accompanying drawings, in theseveral figures of which like reference numerals identify identicalelements, and wherein:

FIG. 1 is a view of the therapeutic end of a typical prior artover-the-wire angioplasty balloon catheter.

FIG. 2 is a side view of a dilating angioplasty balloon catheter withtwo electrodes within the balloon attached to a source of high voltagepulses according to one embodiment of the invention.

FIG. 3 is a schematic of a high voltage pulse generator.

FIG. 3A shows voltage pulses that may be obtained with the generator ofFIG. 3.

FIG. 4 is a side view of the catheter of FIG. 2 showing an arc betweenthe electrodes and simulations of the shock wave flow.

FIG. 5 is a side view of a dilating catheter with insulated electrodeswithin the balloon and displaced along the length of the balloonaccording to another embodiment of the invention.

FIG. 6 is a side view of a dilating catheter with insulated electrodeswithin the balloon displaced with a single pole in the balloon and asecond being the ionic fluid inside the balloon according to a furtherembodiment of the invention.

FIG. 7 is a side view of a dilating catheter with insulated electrodeswithin the balloon and studs to reach the calcification according to astill further embodiment of the invention.

FIG. 8 is a side view of a dilating catheter with insulated electrodeswithin the balloon with raised ribs on the balloon according to stillanother embodiment of the invention.

FIG. 8A is a front view of the catheter of FIG. 8.

FIG. 9 is a side view of a dilating catheter with insulated electrodeswithin the balloon and a sensor to detect reflected signals according toa further embodiment of the invention.

FIG. 10 is a pressure volume curve of a prior art balloon breaking acalcified lesion.

FIG. 10A is a sectional view of a balloon expanding freely within avessel.

FIG. 10B is a sectional view of a balloon constrained to the point ofbreaking in a vessel.

FIG. 10C is a sectional view of a balloon after breaking within thevessel.

FIG. 11 is a pressure volume curve showing the various stages in thebreaking of a calcified lesion with shock waves according to anembodiment of the invention.

FIG. 11A is a sectional view showing a compliant balloon within avessel.

FIG. 11B is a sectional view showing pulverized calcification on avessel wall.

FIG. 12 illustrates shock waves delivered through the balloon wall andendothelium to a calcified lesion.

FIG. 13 shows calcified plaque pulverized and smooth a endotheliumrestored by the expanded balloon after pulverization.

FIG. 14 is a schematic of a circuit that uses a surface EKG tosynchronize the shock wave to the “R” wave for treating vessels near theheart.

FIG. 15 is a side view, partly cut away, of a dilating catheter with aparabolic reflector acting as one electrode and provides a focused shockwave inside a fluid filled compliant balloon.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a view of the therapeutic end of a typical prior artover-the-wire angioplasty balloon catheter 10. Such catheters areusually non-complaint with a fixed maximum dimension when expanded witha fluid such as saline.

FIG. 2 is a view of a dilating angioplasty balloon catheter 20 accordingto an embodiment of the invention. The catheter 20 includes an elongatedcarrier, such as a hollow sheath 21, and a dilating balloon 26 formedabout the sheath 21 in sealed relation therto at a seal 23. The balloon26 forms an annular channel 27 about the sheath 21 through which fluid,such as saline, may be admitted into the balloon to inflate the balloon.The channel 27 further permits the balloon 26 to be provided with twoelectrodes 22 and 24 within the fluid filled balloon 26. The electrodes22 and 24 are attached to a source of high voltage pulses 30. Theelectrodes 22 and 24 are formed of metal, such as stainless steel, andare placed a controlled distance apart to allow a reproducible arc for agiven voltage and current. The electrical arcs between electrodes 22 and24 in the fluid are used to generate shock waves in the fluid. Thevariable high voltage pulse generator 30 is used to deliver a stream ofpulses to the electrodes 22 and 24 to create a stream of shock waveswithin the balloon 26 and within the artery being treated (not shown).The magnitude of the shock waves can be controlled by controlling themagnitude of the pulsed voltage, the current, the duration andrepetition rate. The insulating nature of the balloon 26 protects thepatient from electrical shocks.

The balloon 26 may be filled with water or saline in order to gently fixthe balloon in the walls of the artery in the direct proximity with thecalcified lesion. The fluid may also contain an x-ray contrast to permitfluoroscopic viewing of the catheter during use. The carrier 21 includesa lumen 29 through which a guidewire (not shown) may be inserted toguide the catheter into position. Once positioned the physician oroperator can start with low energy shock waves and increase the energyas needed to crack the calcified plaque. Such shockwaves will beconducted through the fluid, through the balloon, through the blood andvessel wall to the calcified lesion where the energy will break thehardened plaque without the application of excessive pressure by theballoon on the walls of the artery.

FIG. 3 is a schematic of the high voltage pulse generator 30. FIG. 3Ashows a resulting waveform. The voltage needed will depend on the gapbetween the electrodes and generally 100 to 3000 volts. The high voltageswitch 32 can be set to control the duration of the pulse. The pulseduration will depend on the surface area of the electrodes 22 and 24 andneeds to be sufficient to generate a gas bubble at the surface of theelectrode causing a plasma arc of electric current to jump the bubbleand create a rapidly expanding and collapsing bubble, which creates themechanical shock wave in the balloon. Such shock waves can be as shortas a few microseconds.

FIG. 4 is a cross sectional view of the shockwave catheter 20 showing anarc 25 between the electrodes 22 and 24 and simulations of the shockwave flow 28. The shock wave 28 will radiate out from the electrodes 22and 24 in all directions and will travel through the balloon 26 to thevessel where it will break the calcified lesion into smaller pieces.

FIG. 5 shows another dilating catheter 40. It has insulated electrodes42 and 44 within the balloon 46 displaced along the length of theballoon 46.

FIG. 6 shows a dilating catheter 50 with an insulated electrode 52within the balloon 56. The electrode is a single electrode pole in theballoon, a second pole being the ionic fluid 54 inside the balloon. Thisunipolar configuration uses the ionic fluid as the other electrical poleand permits a smaller balloon and catheter design for low profileballoons.

The ionic fluid is connected electrically to the HV pulse generator 30.

FIG. 7 is another dilating 60 catheter with electrodes 62 and 64 withinthe balloon 66 and studs 65 to reach the calcification. The studs 65form mechanical stress risers on the balloon surface 67 and are designedto mechanically conduct the shock wave through the intimal layer oftissue of the vessel and deliver it directly to the calcified lesion.

FIG. 8 is another dilating catheter 70 with electrodes 72 and 74 withinthe balloon 76 and with raised ribs 75 on the surface 77 of the balloon76. The raised ribs 75 (best seen in FIG. 8A) form stress risers thatwill focus the shockwave energy to linear regions of the calcifiedplaque.

FIG. 9 is a further dilating catheter 80 with electrodes 82 and 84within the balloon 86. The catheter 80 further includes a sensor 85 todetect reflected signals. Reflected signals from the calcified plaquecan be processed by a processor 88 to determine quality of thecalcification and quality of pulverization of the lesion.

FIG. 10 is a pressure volume curve of a prior art balloon breaking acalcified lesion. FIG. 10B shows the build up of energy within theballoon (region A to B) and FIG. 10C shows the release of the energy(region B to C) when the calcification breaks. At region C the artery isexpanded to the maximum dimension of the balloon. Such a dimension canlead to injury to the vessel walls. FIG. 10A shows the initial inflationof the balloon.

FIG. 11 is a pressure volume curve showing the various stages in thebreaking of a calcified lesion with shock waves according to theembodiment. The balloon is expanded with a saline fluid and can beexpanded to fit snugly to the vessel wall (Region A)(FIG. 11A) but thisis not a requirement. As the High Voltage pulses generate shock waves(Region B and C) extremely high pressures, extremely short in durationwill chip away the calcified lesion slowly and controllably expandingthe opening in the vessel to allow blood to flow un-obstructed (FIG.11B).

FIG. 12 shows, in a cutaway view, shock waves 98 delivered in alldirections through the wall 92 of a saline filled balloon 90 and intima94 to a calcified lesion 96. The shock waves 98 pulverize the lesion 96.The balloon wall 92 may be formed of non-compliant or compliant materialto contact the intima 94.

FIG. 13 shows calcified plaque 96 pulverized by the shock waves. Theintima 94 is smoothed and restored after the expanded balloon (notshown) has pulverized and reshaped the plaque into the vessel wall.

FIG. 14 is a schematic of a circuit 100 that uses the generator circuit30 of FIG. 3 and a surface EKG 102 to synchronize the shock wave to the“R” wave for treating vessels near the heart. The circuit 100 includesan R-wave detector 102 and a controller 104 to control the high voltageswitch 32. Mechanical shocks can stimulate heart muscle and could leadto an arrhythmia. While it is unlikely that shockwaves of such shortduration as contemplated herein would stimulate the heart, bysynchronizing the pulses (or bursts of pulses) with the R-wave, anadditional degree of safety is provided when used on vessels of theheart or near the heart. While the balloon in the current drawings willprovide an electrical isolation of the patient from the current, adevice could be made in a non-balloon or non-isolated manner using bloodas the fluid. In such a device, synchronization to the R-wave wouldsignificantly improve the safety against unwanted arrhythmias.

FIG. 15 shows a still further dilation catheter 110 wherein a shock waveis focused with a parabolic reflector 114 acting as one electrode insidea fluid filled compliant balloon 116. The other electrode 112 is locatedat the coaxial center of the reflector 114. By using the reflector asone electrode, the shock wave can be focused and therefore pointed at anangle (45 degrees, for example) off the center line 111 of the catheterartery. In this configuration, the other electrode 112 will be designedto be at the coaxial center of the reflector and designed to arc to thereflector 114 through the fluid. The catheter can be rotated if neededto break hard plaque as it rotates and delivers shockwaves.

While particular embodiments of the present invention have been shownand described, modifications may be made. For example, instead of manualactuation and spring loaded return of the valves used herein,constructions are possible which perform in a reversed manner by beingspring actuated and manually returned. It is therefore intended in theappended claims to cover all such changes and modifications which fallwithin the true spirit and scope of the invention as defined by thoseclaims.

What is claimed is:
 1. A catheter comprising: an elongated carrier; aballoon about the carrier in sealed relation thereto, the balloon beingarranged to receive a fluid therein that inflates the balloon; and anarc generator including at least one electrode within the balloon thatforms a mechanical shock wave within the balloon.
 2. The catheter ofclaim 1, wherein the at least one electrode includes a pair of metallicelectrodes.
 3. The catheter of claim 1, wherein the balloon is formed ofnon-compliant material.
 4. The catheter of claim 1, wherein the balloonis formed of compliant material.
 5. The catheter of claim 1, wherein theballoon has a surface, and wherein the catheter further comprises atleast one stress riser carried on the surface of the balloon.
 6. Thecatheter of claim 1, further comprising a sensor that senses reflectedenergy.
 7. The catheter of claim 1, further comprising a reflectorwithin the dilating balloon that focuses the shock waves.
 8. Thecatheter of claim 1, further including a lumen for receiving a guidewire.
 9. A system comprising: a catheter including an elongated carrier,a balloon about the carrier in sealed relation thereto, the balloonbeing arranged to receive a fluid therein that inflates the balloon, andan arc generator including at least one electrode within the balloonthat forms a mechanical shock wave within the balloon and a power sourcethat provides electrical energy to the arc generator.
 10. The system ofclaim 9, wherein the power source is arranged to provide pulsed highvoltage.
 11. The system of claim 10, wherein the power source isarranged to provide high voltage pulses having at least one ofselectable pulse durations, selectable voltage amplitudes, andselectable pulse repetition rates.
 12. The system of claim 9, furthercomprising an R wave detector that synchronizes the mechanical shockwaves with cardiac R waves.
 13. The system of claim 9, wherein thecatheter includes a lumen for receiving a guide wire.
 14. A methodcomprising: providing a catheter including an elongated carrier, aballoon about the carrier in sealed relation thereto, the balloon beingarranged to receive a fluid therein that inflates the balloon, and anarc generator including at least one electrode within the balloon thatforms a mechanical shock wave within the balloon; inserting the catheterinto a body lumen of a patient adjacent to an obstruction of the bodylumen; admitting fluid into the balloon; and applying high voltagepulses to the arc generator to form a series of mechanical shocks withinthe balloon.
 15. The method of claim 14, including the further step ofdetecting cardiac R waves of the patient's heart, and synchronizing themechanical shocks with the detected R waves.
 16. The method of claim 14,including the further step of varying one of the repetition rate,amplitude and duration of the high voltage pulses to vary the intensityof the mechanical shock waves.
 17. The method of claim 14, including thefurther step of sensing reflected energy within the catheter.
 18. Themethod of claim 14, including the further step of placing a guide wireinto the body lumen and guiding the catheter into the body lumen alongthe guide wire.
 19. The method of claim 14 including the further step offocusing the mechanical shockwaves.
 20. The method of claim 14 includingthe further steps of adding an x-ray contrast to the fluid andvisualizing the catheter under fluoroscopy.